Creating another differently formatted js object from an existing js object

Question

I have a function which is returning a js object in this format

{ _id: { day: 21, month: 10, year: 2020 },
  TOTAL: 9,
  A: 4,
  B: 1,
  C: 1,
  D: 2 }

and I have to format the above one into this format:

{ modalities:
   { TOTAL: { '21-09-2020': 2, '20-10-2020': 1, '21-10-2020': 8 },
     A: { '21-09-2020': 1, '21-10-2020': 4 },
     B: { '21-10-2020': 1 },
     C: { '21-09-2020': 1, '21-10-2020': 1 },
     D: { '20-10-2020': 1, '21-10-2020': 2 } } }

as a beginner, I don't have much experience with formatting and right now I'm thinking to implement this with forEach. Is there any better way to do it in javascript?

This is a bit of a tricky "groupBy" operation. Are you certain you want the dates as keys in final output? It doesn't make it any more difficult to create but standardized key names are easier to work with once you have it transformed — charlietfl, Oct 26 '20 at 06:13
Yes, I want this to be specified in that format and I'm not entirely sure how to do it. — Ashish Bairwa, Oct 26 '20 at 06:19

score 1 · Answer 1 · answered Oct 26 '20 at 06:25

let data = [
  {
    "_id": {
      "day": 21,
      "month": 10,
      "year": 2020
    },
    "TOTAL": 9,
    "XR": 4,
    "CT": 1,
    "MR": 1,
    "MG": 2
  },
  {
    "_id": {
      "day": 20,
      "month": 10,
      "year": 2020
    },
    "TOTAL": 1,
    "XR": 0,
    "CT": 0,
    "MR": 0,
    "MG": 1
  },
  {
    "_id": {
      "day": 21,
      "month": 9,
      "year": 2020
    },
    "TOTAL": 2,
    "XR": 1,
    "CT": 0,
    "MR": 1,
    "MG": 0
  }
];

let result = {
    modalities: {
        TOTAL: {},
        XR: {},
        CT: {},
        MR: {},
        MG: {}
    }
};

for (let element of data) {
    let date = element._id.day + '-' + element._id.month + '-' + element._id.year;
    result.modalities.TOTAL[date] = element.TOTAL;
    result.modalities.XR[date] = element.XR;
    result.modalities.CT[date] = element.CT;
    result.modalities.MR[date] = element.MR;
    result.modalities.MG[date] = element.MG;
}

console.log('result: ' + JSON.stringify(result));

sample output

result: {
  "modalities": {
    "TOTAL": {
      "21-10-2020": 9,
      "20-10-2020": 1,
      "21-9-2020": 2
    },
    "XR": {
      "21-10-2020": 4,
      "20-10-2020": 0,
      "21-9-2020": 1
    },
    "CT": {
      "21-10-2020": 1,
      "20-10-2020": 0,
      "21-9-2020": 0
    },
    "MR": {
      "21-10-2020": 1,
      "20-10-2020": 0,
      "21-9-2020": 1
    },
    "MG": {
      "21-10-2020": 2,
      "20-10-2020": 1,
      "21-9-2020": 0
    }
  }
}

It's working, but is there any other workaround other than for and foreach? — Ashish Bairwa, Oct 26 '20 at 06:49
i suppose you can use while loop. or did you want to avoid looping? for loops make the most sense in my opinion — Simon, Oct 26 '20 at 06:53

Jagdish Idhate · Accepted Answer · 2020-10-26T07:56:07.937

1

You can use .reduce as below, by iterating over objects and merging them into single object.

Below code will add any dynamic keys as well, except _id, (if you want you can hardcode keys if you want strict schema).

const temp = [{"_id":{"day":21,"month":10,"year":2020},"TOTAL":9,"XR":4,"CT":1,"MR":1,"MG":2},{"_id":{"day":20,"month":10,"year":2020},"TOTAL":1,"XR":0,"CT":0,"MR":0,"MG":1},{"_id":{"day":21,"month":9,"year":2020},"TOTAL":2,"XR":1,"CT":0,"MR":1,"MG":0}];

const result = temp.reduce((res, obj) => {
  const id = `${obj._id.day}-${obj._id.month}-${obj._id.year}`;
  for (let key in obj) {
    if (key === '_id') // Skip _id, as we don't want in resulting object
      continue;
    if(obj[key]){  // As OP output skips 0 valued keys
      res.modalities[key] = res.modalities[key] || {};
      res.modalities[key][id] = obj[key];
   }
  }
  return res;
}, {modalities:{}});

console.log(result)

edited Oct 26 '20 at 07:56

answered Oct 26 '20 at 07:00

Jagdish Idhate

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Oh, so that's how we can use reduce in this condition. Thanks, that's a good one. – Ashish Bairwa Oct 26 '20 at 07:33
Will you please point out some links where I can get more information around the map and reduce things? – Ashish Bairwa Oct 26 '20 at 08:00
https://medium.com/poka-techblog/simplify-your-javascript-use-map-reduce-and-filter-bd02c593cc2d this may helpful – Jagdish Idhate Oct 26 '20 at 08:05
One last question, what if we want to sort the dates accordingly? – Ashish Bairwa Oct 26 '20 at 10:14
`modalities` and all inside values are `Objects` with key value pairs, javascript keys will not be sorted. You have to either convert them to array then come up with example how do you wanna sort this. Ref: https://stackoverflow.com/questions/1069666/sorting-object-property-by-values – Jagdish Idhate Oct 26 '20 at 10:29

Creating another differently formatted js object from an existing js object

2 Answers2